An acoustic neuroma is a slow-growing tumor of the nerve that connects the ear to the brain. This nerve is called the vestibular cochlear nerve. It is behind the ear right under the brain.
An acoustic neuroma is not cancerous (benign), which means it does not spread to other parts of the body. However, it can damage several important nerves as it grows.
Causes, incidence, and risk factors
Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2).
Acoustic neuromas are relatively uncommon.
Symptoms
The symptoms vary based on the size and location of the tumor. Because the tumor grows so slowly, symptoms usually start after the age of 30.
Common symptoms include:
Abnormal sensation of movement (vertigo)
Hearing loss in the affected ear that makes it hard to hear conversations
Ringing (tinnitus) in the affected ear
Less common symptoms include:
Difficulty understanding speech
Dizziness
Headache
Upon waking up in the morning
Wakes you from sleep
Worse when lying down
Worse when standing up
Worse when coughing, sneezing, straining, or lifting (Valsalva maneuver)
With nausea or vomiting
Loss of balance
Numbness in the face or one ear
Pain in the face or one ear
Sleepiness
Vision problems
Weakness of the face
Signs and tests
The health care provider may diagnose an acoustic neuroma based on your medical history, an examination of your nervous system, or tests.
Often, the physical exam is normal at the time the tumor is diagnosed. Occasionally, the following signs may be present:
The most useful test to identify an acoustic neuroma is an MRI of the head. Other useful tests to diagnose the tumor and tell it apart from other causes of dizziness or vertigo include:
Treatment
Treatment depends on the size and location of the tumor, your age, and overall health. You and your health care provider must decide whether to watch the tumor (observation), use radiation to stop it from growing, or try to remove it.
Many acoustic neuromas are small and grow very slowly. Small tumors with few or no symptoms may be followed, particularly in older patients. Regular MRI scans will be done.
If they are not treated, some acoustic neuromas can damage the nerves involved in hearing and balance, as well as the nerves responsible for movement and feeling in the face. Very large tumors can lead to a buildup of fluid (hydrocephalus) in the brain, which can be life-threatening.
Removing an acoustic neuroma is more commonly done for:
Larger tumors
Tumors that are causing symptoms
Tumors that are growing quickly
Tumors that are growing near a nerve or part of the brain that is more likely to cause problems
Surgery is done to remove the tumor and prevent other nerve damage. Any remaining hearing is often lost with surgery.
Stereotactic radiosurgery focuses high-powered x-rays on a small area. It is considered to be a form of radiation therapy, not a surgical procedure. It may be used:
To slow down or stop the growth of tumors that are hard to remove with surgery
To treat patients who are unable to have surgery, such as the elderly or people who are very sick
Removing an acoustic neuroma can damage nerves, causing loss of hearing or weakness in the face muscles. This damage is more likely to occur when the tumor is next to or around the nerves.
Expectations (prognosis)
An acoustic neuroma is not cancer. The tumor does not spread (metastasize) to other parts of the body. However, it may continue to grow and press on important structures in the skull.
People with small, slow-growing tumors may not need treatment.
Once hearing loss occurs, it does not return after surgery.
Complications
Brain surgery can completely remove the tumor in most cases.
Most people with small tumors will have no permanent paralysis of the face after surgery. However, about two-thirds of patients with large tumors will have some permanent facial weakness after surgery.
Approximately one-half of patients with small tumors will still be able to hear well in the affected ear after surgery.
There may be delayed radiation effects after radiosurgery, including nerve damage, loss of hearing, and paralysis of the face.
Calling your health care provider
Call your health care provider if you experience new or worsening hearing loss, ringing in your ears, or vertigo (dizziness).
References
- Brackmann DE, Arriaga MA. Neoplasms of the posterior fossa. In: Cummings CW, Flint PW, Haughey BH, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, Pa: Mosby Elsevier;2010:chap 177.
- Battista RA. Gamma knife radiosurgery for vestibular schwannoma. Otolaryngol Clin North Am. 2009;42:635-654.
- Sweeney P, Yajnik S, Hartsell W, Bovis G, Venkatesan J. Stereotactic radiotherapy for vestibular schwannoma. Otolaryngol Clin North Am. 2009;42:655-663.
- Conley GS, Hirsch BE. Stereotactic radiation treatment of vestibular schwannoma: indications, limitations, and outcomes. Curr Opin Otolaryngol Head Neck Surg. 2010 Oct;18(5):351-6.
